1 /* 2 * SPDX-License-Identifier: MIT 3 * 4 * Copyright © 2018 Intel Corporation 5 */ 6 7 #ifndef _I915_SCHEDULER_TYPES_H_ 8 #define _I915_SCHEDULER_TYPES_H_ 9 10 #include <linux/list.h> 11 12 #include "gt/intel_engine_types.h" 13 #include "i915_priolist_types.h" 14 15 struct drm_i915_private; 16 struct i915_request; 17 struct intel_engine_cs; 18 19 struct i915_sched_attr { 20 /** 21 * @priority: execution and service priority 22 * 23 * All clients are equal, but some are more equal than others! 24 * 25 * Requests from a context with a greater (more positive) value of 26 * @priority will be executed before those with a lower @priority 27 * value, forming a simple QoS. 28 * 29 * The &drm_i915_private.kernel_context is assigned the lowest priority. 30 */ 31 int priority; 32 }; 33 34 /* 35 * "People assume that time is a strict progression of cause to effect, but 36 * actually, from a nonlinear, non-subjective viewpoint, it's more like a big 37 * ball of wibbly-wobbly, timey-wimey ... stuff." -The Doctor, 2015 38 * 39 * Requests exist in a complex web of interdependencies. Each request 40 * has to wait for some other request to complete before it is ready to be run 41 * (e.g. we have to wait until the pixels have been rendering into a texture 42 * before we can copy from it). We track the readiness of a request in terms 43 * of fences, but we also need to keep the dependency tree for the lifetime 44 * of the request (beyond the life of an individual fence). We use the tree 45 * at various points to reorder the requests whilst keeping the requests 46 * in order with respect to their various dependencies. 47 * 48 * There is no active component to the "scheduler". As we know the dependency 49 * DAG of each request, we are able to insert it into a sorted queue when it 50 * is ready, and are able to reorder its portion of the graph to accommodate 51 * dynamic priority changes. 52 * 53 * Ok, there is now one active element to the "scheduler" in the backends. 54 * We let a new context run for a small amount of time before re-evaluating 55 * the run order. As we re-evaluate, we maintain the strict ordering of 56 * dependencies, but attempt to rotate the active contexts (the current context 57 * is put to the back of its priority queue, then reshuffling its dependents). 58 * This provides minimal timeslicing and prevents a userspace hog (e.g. 59 * something waiting on a user semaphore [VkEvent]) from denying service to 60 * others. 61 */ 62 struct i915_sched_node { 63 struct list_head signalers_list; /* those before us, we depend upon */ 64 struct list_head waiters_list; /* those after us, they depend upon us */ 65 struct list_head link; 66 struct i915_sched_attr attr; 67 unsigned int flags; 68 #define I915_SCHED_HAS_EXTERNAL_CHAIN BIT(0) 69 intel_engine_mask_t semaphores; 70 }; 71 72 struct i915_dependency { 73 struct i915_sched_node *signaler; 74 struct i915_sched_node *waiter; 75 struct list_head signal_link; 76 struct list_head wait_link; 77 struct list_head dfs_link; 78 unsigned long flags; 79 #define I915_DEPENDENCY_ALLOC BIT(0) 80 #define I915_DEPENDENCY_EXTERNAL BIT(1) 81 #define I915_DEPENDENCY_WEAK BIT(2) 82 }; 83 84 #endif /* _I915_SCHEDULER_TYPES_H_ */ 85